An accident caused a train derailment which in turn led to an explosion outside the city of Baltimore, sending a black plume of smoke billowing up into the air.

Local reports indicate that a semi-truck and a CSX cargo train collided, causing several of the trains cars to derail, setting off a massive explosion that was felt several blocks away, WJZ reports.

The accident occurred shortly just after 2 p.m. northeast of Baltimore. Police and fire crews were responding to the area but recent reports indicated that they were prepared to let the fire burn itself out, given that it had not spread to the immediate area.

"We went outside of his house, which is right on the top of Route 40 at Philadelphia Road. We were watching the fire, and then all of a sudden the explosion happened and actually knocked me off my feet. The window broke out in his house. You could feel the heat on our faces. I never seen anything like it," a witness told WJZ.

Baltimore County Police tweeted that several nearby buildings collapsed and Hazmat teams were responding to the scene. Witnesses described feeling the shockwave more than a half mile away.

Reports indicate that at least six rail cars were involved in the derailment. There has been no immediate word regarding the contents of the derailed train cars.